Tuning Neck Clearance Levels

[gmr4]

I’ve watched a YouTube video by Bruce Teal several times where he insists tuning clearance, stepped levels of clearance when turning brass. Bruce speaks of it in a Cortina interview. He shoots 5 shot test groups at difference thickness and swears he sees differences. Anyway I can’t find anything else on the topic. Bruce is a champion so I’m listening as I note / plan my steps to take in tuning…. I’m new to all this and appreciate helpful commentary.

 

[Cloudrepair]

As long as you have clearance in the chamber used .
Actually i think that the chamber dictates the clearance if i understand you right .
I dont really see what changing that much will do it seems we are talking maybe a .002 window that will probably have best results in .002 of finished round neck clearance. Maybe im missing somthing.
Im sure there are many that have a biger window but why, if you can determine that in your reamer or smith?
I am nobody so dont get thinking i have the answers.

 

[gmr4]

As long as you have clearance in the chamber used .
Actually i think that the chamber dictates the clearance if i understand you right .
I dont really see what changing that much will do it seems we are talking maybe a .002 window that will probably have best results in .002 of finished round neck clearance. Maybe im missing somthing.
Im sure there are many that have a biger window but why, if you can determine that in your reamer or smith?
I am nobody so dont get thinking i have the answers.

Thanks for the reply.
My smith says 002. Turn cases properly and go.
Turning 5 cases to .001 then 5 to .002 … 5 to .003 clearance and so on then shooting a test to find what shoots best is the idea even though the reamer is a known dimension. In the video and interview Dave says others don’t do this and win. I may try this step though it seems the same is accomplished with different size bushings - I think.

 

[Tim Singleton]

Thanks for the reply.
My smith says 002. Turn cases properly and go.
Turning 5 cases to .001 then 5 to .002 … 5 to .003 clearance and so on then shooting a test to find what shoots best is the idea even though the reamer is a known dimension. In the video and interview Dave says others don’t do this and win. I may try this step though it seems the same is accomplished with different size bushings - I think.

It’s worth testing to see what your target tells you
Then you can have peace of mind on it
only cost ya 10 pieces of brass mark them and keep for foulers

 

[Mark611]

JMO as well, I think the reamer used should be taken into account here, to determine the amount of clearance needed for proper expansion of the neck for that chamber,

 

[Mark611]

If you go to small your necks won't expand enough to seal the chamber, if you're running a Sami spec chamber? I wouldn't go more than 2k, I just turned some ALFA 308win cases yesterday for my new Criterion Match barrel, I only tuned off 1k to uniform the necks, I did this by measuring some of the cases to find the low spot and marked that spot, then set my cutter to just touch the marked spot, after turning them it was 1k of material that was removed, hopefully tomorrow I can test them,

 

[rwj]

Thanks for the reply.
My smith says 002. Turn cases properly and go.
Turning 5 cases to .001 then 5 to .002 … 5 to .003 clearance and so on then shooting a test to find what shoots best is the idea even though the reamer is a known dimension. In the video and interview Dave says others don’t do this and win. I may try this step though it seems the same is accomplished with different size bushings - I think.

I’m not familiar with the video you’ve cited. But are you certain that subject is neck chamber clearance and not the amount of bullet interference when seated in the case neck? Using different size bushings will only affect the amount of interference when seating the bullet. Chamber neck clearance can only be effected by changing the case neck wall thickness.

 

[expiper]

when you change the neck thickness you should also change the bushing in your resize die --it is more how much tension on the bullet shank than how much clearance,,,,Roger

 

[gmr4]

I’m not familiar with the video you’ve cited. But are you certain that subject is neck chamber clearance and not the amount of bullet interference when seated in the case neck? Using different size bushings will only affect the amount of interference when seating the bullet. Chamber neck clearance can only be effected by changing the case neck wall thickness.

Yes it’s clearance. BT Competition Shooting on YouTube. Then Cortina Bruce Teel on YouTube. I see so many opinions it is hard to determine what to do that COUNTS. Teel is a 3-4 time Long range bench rest shooter so I’m listening close. I am shooting FClass 6.5-7 PRCW or will soon. BRA for now.

 

[ShtrRdy]

I wonder if any difference in results is due to the thickness of the brass at the neck?

 

[RegionRat]

FWIW: This link should take you straight to Bruce's interview at that point where he is discussing the OP's specific question. Bruce is an accomplished LR BR shooter and Erik Cortina is an accomplished F-Open shooter.

 

[BoydAllen]

Thanks for the reply.
My smith says 002. Turn cases properly and go.
Turning 5 cases to .001 then 5 to .002 … 5 to .003 clearance and so on then shooting a test to find what shoots best is the idea even though the reamer is a known dimension. In the video and interview Dave says others don’t do this and win. I may try this step though it seems the same is accomplished with different size bushings - I think.

Neck clearance has absolutely nothing to do with bushing size. It is twice the neck thickness added to the largest diameter of the bullet that is in the neck, subtracted from the actual chamber neck diameter.

 

[gmr4]

FWIW: This link should take you straight to Bruce's interview at that point where he is discussing the OP's specific question. Bruce is an accomplished LR BR shooter and Erik Cortina is an accomplished F-Open shooter.

Bruce is convincing and 3 time BR 600 winner and 1 time at 1000 so I listened and played it over and over trying to understand. I am trying to take information from this type of shooter mostly. I read BS here and there ya know. I think I’ll give it a go as Bruce outlines in other videos.

 

[gmr4]

Neck clearance has absolutely nothing to do with bushing size. It is twice the neck thickness added to the largest diameter of the bullet that is in the neck, subtracted from the actual chamber neck diameter.

I get it but I also know the bushing sqeezes the neck and was thinking it ties together. Appriate your posting. This helps. Thanks

 

[Ccrider]

I get it but I also know the bushing sqeezes the neck and was thinking it ties together. Appriate your posting. This helps. Thanks

How could it not. I think to some extent it is different ways to address the same thing. Using the same bushing, the thinner the neck, the easier it expands and the less hold it places on the bullet.

There is the perfect spot where all is in tune and all the bullets want to go into the same hole.

 

[rwj]

FWIW: This link should take you straight to Bruce's interview at that point where he is discussing the OP's specific question. Bruce is an accomplished LR BR shooter and Erik Cortina is an accomplished F-Open shooter.

Learned something new today!

 

[Big_Daddy]

Myself and a couple of other members here are lucky enough to have Bruce as a member of our local range.
He is definitely a wealth of knowledge and truly a genuinely a nice guy.
Spent a couple of hours at the range with Bruce today.

 

[Ccrider]

Once you turn enough neck off to get full clearance with the particular charge, that will give you the thickest neck that you can run safely. Theoretically, the thickest the neck will provide the most hold on the bullet and reducing neck thickness will reduce bullet hold. That is why some have said they went from 262 to 268 or no turn necks with their PPCs.

Will turning the neck down in .001 steps decrease the amount of hold? I think so. Could you get the same reduction in bullet hold by reducing the bushing size in .001 increments?

Turning the neck down in .001 increments will also reduce your finished round size. In addition to reducing bullet hold, what impact does this have on barrel harmonics?

 

[Tim Singleton]

Once you turn enough neck off to get full clearance with the particular charge, that will give you the thickest neck that you can run safely. Theoretically, the thickest the neck will provide the most hold on the bullet and reducing neck thickness will reduce bullet hold. That is why some have said they went from 262 to 268 or no turn necks with their PPCs.

Will turning the neck down in .001 steps decrease the amount of hold? I think so. Could you get the same reduction in bullet hold by reducing the bushing size in .001 increments?

Turning the neck down in .001 increments will also reduce your finished round size. In addition to reducing bullet hold, what impact does this have on barrel harmonics?

It is a good question.
Does Bruce drop to a smaller bushing as he turns the necks for more clearance in his testing
or continue with the same bushing?

Is it the additional clearance he is seeing on the target, or change in bullet hold?

 

[Flirtinwithdisaster]

Hi Guys, I see lots of questions regarding neck tension, along with clearance. I try to keep each test separate. So when trying to find the proper clearance, I attempt to keep neck tension the same. So yes, I adjust bushings and mandrels to try to keep neck tension the same.
Bruce